(Newbe) 273 to a 340 and tremec 5speed swap.

thing to know is 273 318 340 all internal balance engines should interchange easily I kept a 318 for years as a backup in case my 340 grenaded. I recently built my second 340 and passed the 318 on. 360 youll need a felxplate and converter that works with that external balance setup. Cheapest is a 318 swap.